Patent GB-352947-A (GB)
Title: Improvements in shock absorbers, more particularly for road vehicles
IPC: F16F9/28
Filed: 1930-04-14
Abstract: 352,947. Hydraulic shockabsorbers. WHITTED, J. B., 1826, Diversey Parkway, Chicago, U.S.A. April 14, 1930, No. 11742. [Class 108 (iii).] A shock-absorber for vehicles comprises a cylinder containing liquid, a main piston adapted to be reciprocated therein, and a compensating piston carrying a metering pin registering with a flow control opening in the main piston, the compensating piston being maintained substantially at a predetermined distance from the normal position of the main piston corresponding to a given vehicle load, by the provision of a comparatively weak spring which urges the compensating piston towards the main piston, and by a comparatively strong spring which is associated with means for limiting its expansion and tends to maintain the compensating piston at not less than a predetermined distance from the main piston, means being provided for permitting slow transference of liquid from one side of the compensating piston to the other side. A piston 35, Figs. 1 and 2, is reciprocated in a cylinder 12 (secured to the vehicle body), by means of links 32, a lever 25, a shaft 17, and an arm 27 connected at its end 28 to the vehicle axle &c. In upward movements of the piston, an unrestrained flow of oil is permitted through passages 36 and past a spring-pressed disc valve 50, so that the downward movement of the vehicle body is not retarded. The piston 35 is provided with a plug 45, a central bore 51 in which communicates through a passage 40, vertical grooves in the external wall of a cap 41, a conical recess 43, and a cross bore 44, with the upper part of the cylinder. The bore 51 is provided with a reduced aperture 52, through which passes a metering-pin 53 formed with a reduced portion between larger portions, both of which are tapered upwardly, the arrangement being such that the reduced portion of the pin opposes a reduced resistance to the passage of oil for slight movements of the vehicle body from the normal position, while for the larger movements, the upward or rebound movement is resisted at an increasing rate as the body approaches and recedes from the normal position. Beneath the plug 45 is a perforated cap 67, which is provided with a flanged lower edge to engage a flange on a compensating piston 55 and is pressed upwards by a spring 68, the lower end of which engages the compensating piston 55, which supports the pin 53 and is acted upon by a spring 66 considerably weaker than the spring 68. In downward movements of the piston 35, the cap 67 is forced down into the compensating piston 55, oil passing to the aperture 52 through the perforations in the cap until the plug 45 engages a rim 72 on the upper face of the compensating piston 55, when further movement can only be obtained by a slight forcing down of the piston 55, oil beneath which passes through a small orifice 74 and through grooves in the rim 72 to the aperture 52. In case of variations in the load on the vehicle, the compensating piston 55, and consequently the pin 53, adjust themselves to the correct position under the action of the springs 66, 68; the orifice 74 is, however, too small to allow appreciable movement of the piston 55 under road shocks. In a modification, an additional cylinder and piston are provided, the two pistons being moved in opposite directions by a double-armed lever, and the second piston being controlled by a tapered metering-pin carried by a plate removably fitted in the bottom of the second cylinder, without the use of a compensating piston in this cylinder.